* Batteries for crawler and turntable drive were 6 AA rechargables; I later revised this with some non-LEGO wiring to have a total of 8AA rechargables (9.6V total).

drive paths

CAD view with turntable

building the superstructure

building the superstructure

air pressure switch

actual gears

CAD view w/ turntable drive

building the superstructure

compressor

body panels

Superstructure

The model was designed with all air and electric functions housed in the superstructure. One particularly challenging aspect was having the crawler motors connect mechanically to the crawlers. This linkage had to pass through the turntable. I slightly modified an idea using concentric drive shafts from Jennifer Clark to make this work.

The superstructure ended up crammed full of motors, cables, hoses, etc. and of course the compressor and battery pack. It took me several revisions to make it all work.

There were a total of 4 motors. One for each crawler, one for the turntable, and one for the compressor.

All pneumatic and electric controls were housed in a hand-held box. This box was connected to the model by an umbilical. This umbilical contained 4 electric lines (1 in, 3 out) and 8 air lines (two per boom function) as well as a single air line coming in from the compressor. All pneumatic parts were genuine LEGO pieces, but the electric controls made use of a non-LEGO made switch.

There was a custom-built pressure sensor that would cut the power to the compressor when the pressure maxed out. This made use of the rare and coveted Technic pole reverser :-)

Removeable body panels covered the superstructure and formed the detailed almost-to-scale ""LEGO-fied"" exterior of the model.

boom construction

boom construction

bucket construction

crawler construction

crawler construction

boom construction

boom construction

crawler construction

crawler construction

Digging Boom and Crawlers

The boom was made using a beam and plate style construction. Some of the pneumatic hoses were run through the hollow insides of the boom.

The boom had two main segments plus a bucket at the tip. There were four pneumatic features: boom up and down (the whole boom), second segment up and down, bucket rotation, and bucket open/close.

The operation of the boom was slow. The main boom up/down used 4 LEGO pneumatic cylinders linked together, so it took a relatively large volume to push it.

The crawlers and base of the model was fairly simple. The mechanical drive coming from the superstructure was routed down through the turntable and then out (perpendicular) to the crawler treads.

hand-held controls

umbilical

Model Controls

As explained before, all controls were placed in this hand-held box connected to the model by an umbilical of pneumatic and electric lines. This umbilical turned out to be relatively stiff and heavy, and would hinder the model's performance (i.e. the model would have to drag the heavy umbilical when it rotated (aka "swing") or crawled).

It was neat to have all the controls right at your hands, but the model's performance wasn't great.

The Real R996

Here are photos of the real machine. It's a massive thing weighing in at 741 short tons (shovel version). It has 3000 HP and two V-16 engines. The engines drive hydraulic pumps, and all major functions of the machine are hydraulically powered.